1. Field of the Invention
The present invention relates to a bearing failure judging apparatus and more particularly, to an apparatus for judging the type of a failure occurring in a bearing.
2. Description of the Prior Art
A conventional apparatus is shown in block form in FIG. 1. A sensor/amplifier section (1) detects the vibration of a bearing (not shown) and amplifies the detected signal. The output signal from the sensor/amplifier section (1) is applied to an effective value detecting section (2) where the effective value of the output signal is detected and also to the peak value detecting section (3) where a peak value thereof is detected. The effective value detected is compared with a set value previously set in an effective value comparator (4) to judge whether the effective value is normal or not. Similarly, the peak value detected is compared with a set value previously set in a peak value comparator (5) to judge whether the peak value is normal or not. A judging section (6) judges on the basis of the results of the comparisons whether the bearing has failed. A display section (7) displays the result of the judgement by the judging section (6). When the judging apparatus described above determines that the bearing is abnormal, the judging apparatus encounters many problems in seeking what type of failure renders the bearing abnormal. The first problem is involved in the values obtained by the effective value and peak value detecting sections. Particularly the peak value varies largely with the frequency components of the waveform of the detected signal, possibly leading to an error of the peak value. The second problem is the erroneous operation of the judging apparatus. Generally, the bearing failure judging apparatus is with coupled to a dynamically operating equipment containing the bearing, so that pulsate waves occurring at the start and the stop of the equipment or disturbances caused during maintenance, drive the judging apparatus as if a failure is present in the bearing. The third problem is involved with the discriminating ability of the judging apparatus for discriminating the cause of the failure. There is a suggestion that the cause of the failure due to scars or other causes may be quantitatively judged on the basis of the ratio of the effective value to the peak value. The suggestion lacks a quantitative analysis and therefore the judgement thereby is frequently erroneous. In order to solve these problems, the following prior art (Japanese Patent Application No. 4531/1978) has been proposed and has solved some of the problems successfully. The prior art will be described in reference to FIG. 2. As shown, a sensor/amplifier section (1) is connected at the output to a low-pass filter (8) which is further connected at the output to an A/D converter (9). A control section (10) is connected to a memory section (11) and an arithmetic logic section (12) is connected at the output to a display section (7). In the device shown in FIG. 2 which is designed to the sense scars of a bearing, a signal wave is digitized by the A/D converter (9), controlled by the control section (10), loaded into or read out from the memory section (11), and applied to the arithmetic logic section (12) where it is subjected to a Fourier conversion to extract features of the sensed signal in the frequency domain. Through the processings, the kind and a degree of the scars occuring at the respective portions of the bearing are classified and analyzed and then displayed in the display section (7). The judging apparatus thus described provides very useful data of a specific failure, or the scar of the bearing.